Three models were compared (see Figure 2, below). Model 1 was the simplest and included current depression symptoms from the BDI-II, stimulant dependence symptoms, disease severity (CD4+cell count), and use of protease inhibitors as predictors. Model 2 was similar. However, it combined depression symptoms and stimulant dependence symptoms with one additional variable, childhood conduct disorder problems, to represent a single unifying hypothetical construct—mood dysregulation. Model 3 was identical to Model 2 but added anterior region CNV amplitude (a neurophysiological indicator of “impatience”) as a factor through which the effects of mood dysregulation were mediated. For each of the three models, the discrepancy χ2 index for model fit was evaluated. In addition, the adequacy of each model fit was evaluated by the Root Mean Square Error of Approximation (RMSEA) and Adjusted Global Fit Indices (AGFI), which are less distorted than the discrepancy index by a moderate sample size and the complexity of the model.
